One or more hydrocarbon bearing zones within a wellbore often need to be isolated from other portions of the wellbore. An effective solution for zonal isolation is the use of swellable packers. However, controlling the swelling rate of the swellable material that forms the sealing element of the swellable packer is important. If the swell rate of the swellable material is too slow, the setting of a completion within the wellbore will take too long, which unnecessarily increases costs, including rig time and personnel. If the swell rate of the swellable material is too rapid, the swellable packer can set the completion within the wellbore before the completion is properly located within the wellbore.
Furthermore, swellable materials with faster swelling rates often have a higher final swell percentage, and materials with slower swelling rates often have a smaller final swell percentage. Accordingly, if a large final swell percentage is desired, the swell rate of the swellable material may make it impossible to completely run the completion into the wellbore. One method of controlling swelling rates of swellable materials is to encapsulate the swellable material in a material having a slower swell rate, which prevents the fluid from reaching the swellable material until the slower swell rate material is either dissolved or saturated. This method is problematic because the material with the slower swell rate can be damaged while being run into the wellbore, and the fluid can reach the faster swell rate material faster than expected. As such, the faster swell rate material can start swelling sooner than expected, and the completion can be prematurely secured within the wellbore.
A need exists, therefore, for apparatus and methods that can predictably retard the swell rate of a high swell percentage material for a predetermined time and allow for the swellable element to reach the full swell percentage of the swellable material after a predetermined time.